Please referring to FIG. 1, a conventional sealed zipper bag 1 has an air valve 2 bonded thereon and can be sealed after food has been filled inside, then superfluous air can be sucked out through an air suction member (not shown in the drawing) via the air valve 2 to make the interior of the zipper bag 1 in a vacuum state to prevent oxidization or damping of the food to increase food preservation period.
The zipper bag 1 can also receive injection of inertia fresh-keeping gas such as nitrogen via a gas injection member (not shown in the drawing) through the air valve 2 to reduce food rotten speed and help to maintain freshness of the food.
Depending on different requirements of air suction or gas injection the air valve 2 can be selected a two-way valve to meet air suction or injection requirement, or an one-way air valve, and is bonded to the zipper bag 1 in a selected direction to improve air suction or injection efficiency, and also enhance air-tightness to fully meet use requirements.
While the aforesaid conventional technique can make the zipper bag 1 vacuum or inject gas inside to meet use requirements, due to airtight concern the air valve 2 and the zipper bag 1 often are fixedly fastened by bonding. When the zipper bag 1 cannot be reused and has to be thrown away, the air valve 2 also is discarded. This not only creates environmental concern, also increases the fabrication cost of the zipper bag 1 equipped with the air valve 2. As a result, the price is higher and use requirements cannot be fully met.